Google was the biggest donor at the annual fundraising dinner last year of the Competitive Enterprise Institute, a Washington-based group that opposes government policies to cut carbon emissions. The dinner was headlined by tea-party-aligned Sen. Rand Paul (R., Ky.). Google donated $50,000, according to the invitation and information from the group.

Google also gave what it terms "substantial support" to other conservative and libertarian groups, including the Heritage Foundation, the American Enterprise Institute and Americans for Tax Reform. It gives the libertarian Cato Institute $480,000 worth of free web advertising annually, according to Cato. It gave the Federalist Society as much as $49,000 last year, the group said.

It provided support to Heritage Action, which helped lead the charge to defund the 2010 health-care law that prompted October's partial government shutdown; to the American Conservative Union, which runs the annual CPAC conference, a landmark on the conservative calendar; and to the American Legislative Exchange Council, which writes model conservative legislation for states and has drawn criticism from the left.

To be sure, Google gives to a range of liberal-leaning organizations, such as the Center for American Progress, which has close ties to the Obama administration. It has also given to the Congressional Black Caucus Foundation.